Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$181.58	10.406%	$200.4752	$200.48	$200.50	$200.50
Purchase #2	$111.64	13.779%	$127.0229	$127.02	$127.00	$127.00
Purchase #3	$50.72	13.762%	$57.7001	$57.70	$57.70	$57.70
Purchase #4	$152.91	11.221%	$170.068	$170.07	$170.05	$170.10
Purchase #5	$157.96	13.293%	$178.9576	$178.96	$178.95	$179.00
Purchase #6	$131.42	9.401%	$143.7748	$143.77	$143.75	$143.80
Purchase #7	$113.86	10.187%	$125.4589	$125.46	$125.45	$125.50
7 purchase totals =	$900.09		$1,003.4575	$1,003.46	$1,003.40	$1,003.60